The present invention generally relates to oxygen delivery systems and, more particularly, to an improved portable system having an extended use time for efficiently delivering vaporized liquid oxygen to a patient.
Oxygen delivery systems are used in a wide variety of applications. Liquid oxygen delivery systems have the advantage that a much greater quantity of oxygen can be stored in liquid form than can be stored as a gas. The liquid oxygen can be delivered to a use device in that form or can be converted to a gas and then delivered.
An exemplary liquid oxygen delivery system is a portable oxygen delivery apparatus which vaporizes liquid oxygen and delivers the resulting vapor to a patient via a cannula. This type of system typically consists of a portable, thermally insulated tank for holding a quantity of liquid oxygen. A dip tube extends into the tank and conveys the liquid to a vaporizer coil for conversion to a gas. An adjustable flow control valve permits the patient to control the flow of oxygen gas from the vaporizer to the cannula.
High efficiency vaporizers are desirably used in liquid oxygen delivery systems for quickly vaporizing a desired volume of liquid oxygen. High volume vaporization is generally beneficial so that oxygen flow requirements can be promptly satisfied. However, it will be appreciated that when vapor production exceeds the demand for oxygen vapor, an increase in tank pressure results creating a significant back pressure in the tank. When the pressure reaches a predetermined maximum, a relief valve opens to vent oxygen to the atmosphere. While venting maintains the system pressure within acceptable limits, it is wasteful and significantly shortens the use time of the delivery system.
Accordingly, an efficient delivery system for cryogenic liquids having an extended use time and that minimizes pressure build-up from excess vaporization is desired.